Hillary Clinton got nicked Tuesday evening in Philadelphia - as much by herself as by any of the other candidates in the Democratic primary debate. It's hardly mortal, but her experience is at least instructive, especially given the modern historical imperative that leading nomination-seekers endure a near-death experience at some point, if not always the real thing.

Clinton got nicked because she screwed up on two little things and two big things: the secreted White House documents from Bill Clinton's administration; driver's licenses for undocumented immigrants in New York; the war in Iraq; and the looming whatever in Iran.

She remains much more than a formidable figure, however, in part because she is only half-wrong on Iran and because on the other major topic of the evening - social security's uncertain future - she happens to be substantively correct and politically near-perfect.

Clinton and the rest of us also got to see a demonstration of another meaning of the buzzword triangulation. In addition to the Clintonian concept of angle-playing with big issues, there is also a political-tactical meaning - on vivid display Tuesday: Candidate A (that would be John Edwards) strongly criticizes Candidate B (Clinton); but it is the less forceful, more cerebral fellow (as in Barack Obama) who benefits in the short run.

Little things can matter in raised-profile debates if they work as metaphors. Trimming, for example, is a lousy trait always, and Clinton trimmed big-time in trying to paint the matter of her husband's documents as a smoothly unfolding bureaucratic process in which she is somehow passive but cooperative. The national archives has the letter from her husband putting his stuff, especially her memos to him, off limits until the end of her presumptive first term in 2012. Naughty, naughty.

And if angle-playing is a disturbing family trait, she put it on truly graphic display when asked if she supports New York governor Eliot Spitzer's notion of making a special kind of license available to the undocumented. In one rambling exchange, she went from conditional approval to conditional disapproval to the resolutely non-committal. Edwards had the sense to call her out on her gymnastics, so compellingly that Obama felt obliged to chime in.

While revealing, these slip-ups don't hold a candle to getting stuck supporting a residual combat force in Iraq. Edwards managed to communicate clearly, directly and succinctly that if you want a combat force of unknown size for an unknown number of years costing an unknown number of billions of dollars, she's the candidate. Those who support stopping the combat and getting all such forces out within a year or less (above all Edwards and Bill Richardson) now have the chance to make this fundamental difference a voting issue in the campaign. This issue cannot work for Obama, who supports a post-2008 scheme similar to Clinton's, but it worthy of a serious discussion before people start voting.

On Iran, Clinton was unsuccessful in getting away with an argument that the senate resolution branding the country's Revolutionary Guard both a terrorism supporter and a WMD proliferator was just about semantics. The rest of the field unanimously trumped her with the argument that the resolution is a war justification in waiting and that after 2002's congressional acquiescence it is a de facto confession that nothing was learned about blank-check writing.

She was also unsuccessful in trying to triangulate with her support for another resolution introduced by senator Jim Webb of Virginia to the effect that President Bush has no authority to attack Iran and must seek in from Congress before doing so. Because the resolution has no chance whatsoever of passage it counts only for political cover, and cannot excuse a vote for a resolution that could make another unilateral assault easier.

Where she had a point, and as always presented it cogently, is in her argument that if diplomacy is to work, both Congress and the country's allies need to support a graduated escalation of sanctions - the latest batch of which were imposed just last week - to serve as the stick to achieve a bomb-free Iran without violence. Many Democrats, notably Edwards, had also slammed the sanctions. A telling point.

Even more telling were her sound comments on social security. Obama and Edwards went beyond the facts to falsely accuse her of saying one thing in debates and on the trail (a non-committal nothing) about raising the $90,000-plus income ceiling on payroll taxes while being overheard by a reporter in Iowa telling a voter she is open to the idea. It is a distinction without a substantive difference and makes her opponents look shrill.

She is also correct in resisting the conservative-influenced fiction that the system faces a crisis. A return to sane budget policies could mean, she sensibly argued, a return to surpluses and to paying down the national debt, thus giving politics perhaps five decades for the tried-and-true mechanism of bipartisan negotiation about benefits and revenues. In the meantime, nothing is ruled in or out. She wins a social security fight among Democrats strictly on the merits, and wins it hands down on the politics.

But Tuesday showed her weaknesses as well. There is plenty of time for an issue (and not a character) campaign to get traction this month before the December sprint to Iowa. Whether it does is up to her hitherto undisciplined opponents.